# By what mechanism does coffee=\>BM? (Possible TMI) **URL:** \ **Category:** Factual Questions\ **Created:** [July 14, 2006, 2:00pm UTC](https://boards.straightdope.com/t/by-what-mechanism-does-coffee-bm-possible-tmi/364466 "2006-07-14T14:00:15Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![groo](https://avatars.discourse-cdn.com/v4/letter/g/ecd19e/32.png) [@groo](https://boards.straightdope.com/u/groo)\ **Post date:** [July 14, 2006, 2:00pm UTC](https://boards.straightdope.com/t/by-what-mechanism-does-coffee-bm-possible-tmi/364466/1 "2006-07-14T14:00:15Z")
Inspired by [this thread on “BM cycle time”](http://boards.straightdope.com/sdmb/showthread.php?t=379478), I want to know: What is the mechanism by which I can **guarantee** that I’ll take a nice big dump about 45 minutes after my two cups of strong coffee each morning? I know: coffee is a diuretic. But what does that mean? Does the coffee somehow send my GI tract into peristaltic spasms? Does it somehow flip a switch that signals my large intestine to go for it? With me, it’s a dramatic thing. I’ll be sitting in front of my computer, feeling like I’m a million miles away from my next BM, when all of a sudden, my bowels will assert themselves and I’ll want to sound a klaxon, because it’s gonna happen **Real Soon Now**. Actually, I’d like to own a klaxon just for that purpose, but that’s for another thread. Somewhat related to the thread above, does that beautiful, dangerous mystery known as coffee somehow slide around the rest of the solid stuff and rocket towards my colon to smooth the way? Just curious. I’d appreciate any answers, even those that cannot be cited – I think the paucity of information about this matter may be the result of conspiracies centered around the large coffee cartels. ---
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [July 14, 2006, 2:50pm UTC](https://boards.straightdope.com/t/by-what-mechanism-does-coffee-bm-possible-tmi/364466/2 "2006-07-14T14:50:25Z")
Coincidence of timing. You would feel the urge for a bowel movement even if you didn’t drink coffee one morning. Healthy bowels are like that; every day at the same time. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [July 14, 2006, 2:53pm UTC](https://boards.straightdope.com/t/by-what-mechanism-does-coffee-bm-possible-tmi/364466/3 "2006-07-14T14:53:30Z")
Hey, groo. Just sayin’ “hey.” Are you the same groo from a.f.c-a? --Jeff The diuretic part is due to how caffeine acts on the kidneys, probably unrelated to your experience with its laxative properties. A diuretic increases the amount of urine. ---
**Author:** ![daffyduck](https://avatars.discourse-cdn.com/v4/letter/d/ec9cab/32.png) [@daffyduck](https://boards.straightdope.com/u/daffyduck)\ **Post date:** [July 14, 2006, 3:13pm UTC](https://boards.straightdope.com/t/by-what-mechanism-does-coffee-bm-possible-tmi/364466/4 "2006-07-14T15:13:57Z")
The laxative effect of coffee is known. Most associate it with the caffeine. [http://coffeescience.org/media/anticancer](http://coffeescience.org/media/anticancer) It often, but not always, has the same effect on me. ---
**Author:** ![Excalibre](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@Excalibre](https://boards.straightdope.com/u/Excalibre)\ **Post date:** [July 14, 2006, 3:20pm UTC](https://boards.straightdope.com/t/by-what-mechanism-does-coffee-bm-possible-tmi/364466/5 "2006-07-14T15:20:30Z")
[QUOTE=Fear Itself] Coincidence of timing. You would feel the urge for a bowel movement even if you didn’t drink coffee one morning. Healthy bowels are like that; every day at the same time. [/QUOTE] You’re joking, right? The idea that a healthy bowel is precisely set to a 24 hour cycle is a ridiculous old myth that sprang up during the poop-obsessed days of patent medicines, if not before. It has absolutely no significance in the real world. Besides, coffee’s laxative effects are well-known and obvious to anyone who drinks much of it. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [July 14, 2006, 3:29pm UTC](https://boards.straightdope.com/t/by-what-mechanism-does-coffee-bm-possible-tmi/364466/6 "2006-07-14T15:29:00Z")
[QUOTE=Excalibre] The idea that a healthy bowel is precisely set to a 24 hour cycle is a ridiculous old myth that sprang up during the poop-obsessed days of patent medicines, if not before. It has absolutely no significance in the real world. [/QUOTE] It may not be a yardstick by which to say a bowel is healthy, but I for one get the call of nature within +/- 30 minutes the same time every day where one minute I’m reading about the Nationals latest ass-kicking and with almost no notice, the next minute I’m in the can. I don’t drink coffee. ---
**Author:** ![lieu](https://avatars.discourse-cdn.com/v4/letter/l/c2a13f/32.png) [@lieu](https://boards.straightdope.com/u/lieu)\ **Post date:** [July 14, 2006, 3:39pm UTC](https://boards.straightdope.com/t/by-what-mechanism-does-coffee-bm-possible-tmi/364466/7 "2006-07-14T15:39:35Z")
Surely I’m not the only one now humming some Humble Pie… _Back Coffee_ and _Thirty days in the hole._ ---
**Author:** ![spingears](https://avatars.discourse-cdn.com/v4/letter/s/ebca7d/32.png) [@spingears](https://boards.straightdope.com/u/spingears)\ **Post date:** [July 14, 2006, 3:55pm UTC](https://boards.straightdope.com/t/by-what-mechanism-does-coffee-bm-possible-tmi/364466/8 "2006-07-14T15:55:25Z")
[QUOTE=Excalibre] Besides, coffee’s laxative effects are well-known and obvious to anyone who drinks much of it. [/QUOTE] There are a few exceptions. I know folks who drink nothing but coffee and are continuously experiencing constipation. Substitue a full 8 oz. glass of hot water for the morning coffee. Most of the time it will have the same effect! ---
**Author:** ![groo](https://avatars.discourse-cdn.com/v4/letter/g/ecd19e/32.png) [@groo](https://boards.straightdope.com/u/groo)\ **Post date:** [July 14, 2006, 4:48pm UTC](https://boards.straightdope.com/t/by-what-mechanism-does-coffee-bm-possible-tmi/364466/9 "2006-07-14T16:48:48Z")
[QUOTE=CookingWithGas] Hey, groo. Just sayin’ “hey.” Are you the same groo from a.f.c-a? --Jeff The diuretic part is due to how caffeine acts on the kidneys, probably unrelated to your experience with its laxative properties. A diuretic increases the amount of urine. [/QUOTE] Hmm. American Football Coaches Association? Alberta Fire Chiefs Association? Sorry; nothing rings a bell. I didn’t think that coffee being a laxative was even a question. It seems obvious to me, but then again, maybe I’m just mistaking correlation with causation. I’ll try an experiment where I secretly replace my Folgers with an equal amount of water. But I warn you – if water doesn’t do the trick, I’ll be very cross. I was actually hoping that some scientifical type person could drop by and say something along the lines of, “well, the blahdeblah quickly surrounds the stool with a coating of blahdeblah, which aside from being a lubricant also signals the muscles to contract, thus imparting a velocity of bumpty-bum meters per second, resulting in good rapid movement and clean separation” (Or something like that … I also have a question about discrete stools vs. pinched-off, but I wanted to have a thread with a modicum of decorum). ---
**Author:** ![Excalibre](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@Excalibre](https://boards.straightdope.com/u/Excalibre)\ **Post date:** [July 14, 2006, 4:58pm UTC](https://boards.straightdope.com/t/by-what-mechanism-does-coffee-bm-possible-tmi/364466/10 "2006-07-14T16:58:35Z")
[QUOTE=CookingWithGas] It may not be a yardstick by which to say a bowel is healthy, but I for one get the call of nature within +/- 30 minutes the same time every day where one minute I’m reading about the Nationals latest ass-kicking and with almost no notice, the next minute I’m in the can. I don’t drink coffee. [/QUOTE] That’s very nice. I’m happy for your achievement. ---
**Author:** ![iamthewalrus\_3](https://avatars.discourse-cdn.com/v4/letter/i/258eb7/32.png) [@iamthewalrus\_3](https://boards.straightdope.com/u/iamthewalrus_3)\ **Post date:** [July 14, 2006, 5:17pm UTC](https://boards.straightdope.com/t/by-what-mechanism-does-coffee-bm-possible-tmi/364466/11 "2006-07-14T17:17:44Z")
[QUOTE=Fear Itself] Coincidence of timing. You would feel the urge for a bowel movement even if you didn’t drink coffee one morning. Healthy bowels are like that; every day at the same time. [/QUOTE] Not the case for me. I rarely drink coffee in the morning. I usually either drink tea, water, or something sugary that’s bad for me. Coffee is the only one that has this effect. Of course, since I’ve noticed it, this could be psychological. ---
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [July 14, 2006, 5:24pm UTC](https://boards.straightdope.com/t/by-what-mechanism-does-coffee-bm-possible-tmi/364466/12 "2006-07-14T17:24:07Z")
[QUOTE=Excalibre] You’re joking, right? [/QUOTE] They don’t call it regularity for nothing. ---
**Author:** ![groman](https://avatars.discourse-cdn.com/v4/letter/g/73ab20/32.png) [@groman](https://boards.straightdope.com/u/groman)\ **Post date:** [July 14, 2006, 6:06pm UTC](https://boards.straightdope.com/t/by-what-mechanism-does-coffee-bm-possible-tmi/364466/13 "2006-07-14T18:06:09Z")
I don’t know, why would this be obvious? I don’t think caffeine has a laxative effect on me at all to any degree. I don’t know about others, but I have consumed up to 2g of caffeine a day with no changes in the lower gastrointestinal system. Heartburn and such, of course, but nothing below the stomach. ---
**Author:** ![samm](https://avatars.discourse-cdn.com/v4/letter/s/858c86/32.png) [@samm](https://boards.straightdope.com/u/samm)\ **Post date:** [July 14, 2006, 6:55pm UTC](https://boards.straightdope.com/t/by-what-mechanism-does-coffee-bm-possible-tmi/364466/14 "2006-07-14T18:55:19Z")
[Here](http://boards.straightdope.com/sdmb/showpost.php?p=7488668&postcount=14) I posted one possible explanation. But note that “Health Systems International” is suspect and is trying to paint coffee as evil so it may be wildly inaccurate. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [July 15, 2006, 2:36am UTC](https://boards.straightdope.com/t/by-what-mechanism-does-coffee-bm-possible-tmi/364466/15 "2006-07-15T02:36:38Z")
[QUOTE=Excalibre] That’s very nice. I’m happy for your achievement. [/QUOTE] Thank you very much. I enjoyed your citeless refutation. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [July 15, 2006, 2:38am UTC](https://boards.straightdope.com/t/by-what-mechanism-does-coffee-bm-possible-tmi/364466/16 "2006-07-15T02:38:08Z")
[QUOTE=groo] Hmm. American Football Coaches Association? Alberta Fire Chiefs Association? Sorry; nothing rings a bell. [/QUOTE] There is a guy on the usenet newsgroup alt.fan.cecil-adams who goes by “groo”. ---
**Author:** ![Khampelf](https://avatars.discourse-cdn.com/v4/letter/k/8e7dd6/32.png) [@Khampelf](https://boards.straightdope.com/u/Khampelf)\ **Post date:** [July 15, 2006, 4:30am UTC](https://boards.straightdope.com/t/by-what-mechanism-does-coffee-bm-possible-tmi/364466/17 "2006-07-15T04:30:33Z")
I had some extra strong coffee today, and my bowels violently evacuated themselves around 10am, in fact (just to make this definately a TMI thread) as a precursor to this violent and extra loose evacuation I had a “Very Wet Fart” as described in the “Have you ever shit your pants?” thread. I searched for that thread, but could not find it. Anyway, fortunately I was at home and easily changed my shorts. So, anecdotally, the stronger the coffee, the stronger the laxative effect. I drink normal coffee all day long and it doesn’t effect me like that. ---
**Author:** ![Savannah](https://avatars.discourse-cdn.com/v4/letter/s/b3f665/32.png) [@Savannah](https://boards.straightdope.com/u/Savannah)\ **Post date:** [July 15, 2006, 5:12am UTC](https://boards.straightdope.com/t/by-what-mechanism-does-coffee-bm-possible-tmi/364466/18 "2006-07-15T05:12:08Z")
I drink two mugs of hot, strong tea every morning. It’s the tea that gets my trains leaving the station. No tea, no rail service, usually. ---
**Author:** ![Excalibre](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@Excalibre](https://boards.straightdope.com/u/Excalibre)\ **Post date:** [July 15, 2006, 11:52pm UTC](https://boards.straightdope.com/t/by-what-mechanism-does-coffee-bm-possible-tmi/364466/19 "2006-07-15T23:52:33Z")
[QUOTE=CookingWithGas] Thank you very much. I enjoyed your citeless refutation. [/QUOTE] I wasn’t refuting anything. You piped up to describe how regular your bowels are. I congratulated you. It’s obviously something you take a great deal of pride in. What the hell would there be for me to refute? I don’t know your bowel habits. I already know more than I want to. Why the hell would I argue with your claims about how frequently you shit? ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [July 18, 2006, 10:10pm UTC](https://boards.straightdope.com/t/by-what-mechanism-does-coffee-bm-possible-tmi/364466/20 "2006-07-18T22:10:37Z")
[QUOTE=Excalibre] I wasn’t refuting anything. You piped up to describe how regular your bowels are. I congratulated you. It’s obviously something you take a great deal of pride in. What the hell would there be for me to refute? [/QUOTE] Your initial post > [@Excalibre](#): > > The idea that a healthy bowel is precisely set to a 24 hour cycle is a ridiculous old myth that sprang up during the poop-obsessed days of patent medicines, if not before. It has absolutely no significance in the real world. is the refutation I’m referring to. You lambasted **Fear Itself** without providing any facts. Well, I provided a fact. Anecdotal, but at least it’s a fact. It was relevant to the discussion. Your “congratulations” had a distinct sarcastic odor. If you don’t want to read about bowel movement then you should avoid opening threads with “BM” in the title. 😃 Here’s a [good site for this topic](http://health.msn.com/centers/ibdcrohns/articlepage.aspx?cp-documentid=100098792), which has information that agrees with **Fear Itself** > [@](#): > > The urge to defecate is often strongest in the morning: Just getting up triggers the movement of the large intestine. The stomach also sends a signal when it expands after a meal. This gastrocolic reflex is the reason many people, and especially children, need to go to the bathroom soon after eating. , although it also says that bowel movements need not be daily to be healthy. > [@](#): > > In Western societies, people generally defecate two or three times a day, but it’s an individual matter. All the advice about the importance of regular bowel movements notwithstanding, some people defecate just once a week and are perfectly healthy. [Next page](https://boards.straightdope.com/t/by-what-mechanism-does-coffee-bm-possible-tmi/364466.md?page=2)